Parasitic Load with Use/Store Switch in Store

[bevedfelker]

We've had a lot of discussion on the forum regarding house batteries discharging. Has anyone researched exactly what parasitic load is on the house batteries when disconnected with the use/store switch in store. On my 2015 Vegas with the switch in Store none of my interior lights will come on, the radio will not work, there is no current on the USB connection under the radio, none of my CO or fire detectors work, the led light on the antenna booster is out.

So for all intents and purposes my house batteries act like they are completely isolated. I have not checked to see if my radio clock stays updated.

Does anyone know of any other load that could drain the batteries while the switch is in Store. My coach has been stored for 5 weeks and when I check the batteries still have all the lights come on the status panel showing full charge.

[Oneilkeys]

On my 2014 Axis, I installed a permanent volt meter which gave a reading in .00 volts. I also installed a kill switch for the Jensen radio and a Blue Sea on/off switch which completely disconnected the house batteries. When I turned the use/store switch to "store" and left the radio kill switch "on" and the Blue Sea "on" the house batteries still discharged at a rate of several tenths of a volt a week. When I turned the Blue Sea switch to off, the house batteries would keep their charge indefinitely. With the Blue Sea off, the radio was turned completely off and lost its time setting. With the use/store switch in "store" the radio clock continued to work and the radio did not lose its settings. When I used the radio kill switch, with the use/store in "store" the coach batteries still discharged, but at a much slower rate.

So, I concluded that a large part, but not all of the parasitic drain came from the radio. When I dry camped, the radio kill switch made a big difference. When the coach was stored using the use/store switch and not the radio kill switch, it was not enough to stop the batteries from slowly discharging.

Interestingly, Thor seems to have solved the problems in the 2016 model. The store/use switch really works and the radio turns completely off, but does not lose its settings. I don't know if the radio has an internal battery or if the drain is so small that it does not discharge the house batteries.

It doesn't look like I will have to install a true On/off switch or a radio kill switch.

[Bobm1964]

Does anyone use the master kill switch attached to the house batteries?

[Oneilkeys]

Do you mean the circuit breaker on the left hand side of the battery box?

[Bobm1964]

Yes..

[Oneilkeys]

It could be used to disconnect the house batteries from the coach but I don't like sticking my fingers down into the battery box with everything connected. I installed an on/off switch designed for that purpose instead. Interestingly, there is now a second such switch attached to the engine battery in my 2016 Axis.

[BCRacing24]

2014 Thor Class-C

There are 3 wires on the back of my Jensen dash radio.
Red - 12v power(Coach)
Yellow - 12v memory(chassis)
Black - ground

The radio when powered on runs off the Coach batteries (red wire)

When powered off or Coach batteries disconnected via switch the Jensen unit uses the 12v memory wire (yellow) to maintain clock, radio & audio presets. This wire is connected to the chassis battery.....

At least on my Coach anyway.

[Bobm1964]

This is the switch I was talking about.

[Oneilkeys]

Originally Posted by Bobm1964

This is the switch I was talking about.

That is a true on/off switch for the coach batteries. I installed one very similar to that in my Vegas because it didn't have one. Do you also have a "use/store switch" in your coach! I have never seen a switch like yours in an RV. Every RV should come equipped with one. The "use/store" switch is supposed to perform that function if it is installed correctly. In the Vegas/Axis there is a circuit breaker with a little red button installed in the left side of the battery box. That is what I thought you were referring to.

[Oneilkeys]

Originally Posted by BCRacing24

2014 Thor Class-C

There are 3 wires on the back of my Jensen dash radio.
Red - 12v power(Coach)
Yellow - 12v memory(chassis)
Black - ground

The radio when powered on runs off the Coach batteries (red wire)

When powered off or Coach batteries disconnected via switch the Jensen unit uses the 12v memory wire (yellow) to maintain clock, radio & audio presets. This wire is connected to the chassis battery.....

At least on my Coach anyway.

Thank you for that useful information. All of a sudden everything comes together. This apparently is just another in a line of items that Thor installed incorrectly in my 2014 Vegas. When pulled my Jensen radio to install a "kill" switch, I noticed that the red and yellow wires were attached to the same wire. I never thought anything about it. Apparently, instead of wiring it correctly, Thor took the easy way out and wired both the red and yellow wire directly to the coach batteries so that the radio would not lose its settings every time you used the store switch. That is why the radio never turned off and ran down the coach batteries. Since I still had a drain after I installed the radio kill switch, they must have also wired something else directly the coach batteries, bypassing the Use/store switch - but I never figured out what.

My 2016 Axis seems to be wired correctly and there is no drain on the coach batteries when the use/store switch is in the store position.

[FW28z]

Just to clarify a bit, the Red/Yellow/Black power leads on a stereo are pretty much standard.

However, the Yellow wire is a constant source, meaning the radio is always energized when powered. This wire typically is also the main power lead, AND since it is always energized, it also provides memory.

The Red wire goes to the ignition, and puts the radio from standby to active when on. It is not the main (i.e. heavy current carrying) power wire, it is the power switch wire.

The dead giveaway is that the Yellow wire is often (but not always) a heavier gauge wire than the Red wire. Of course, both Red and Yellow need to be energized for the stereo to operate.

The only really good way to determine if you have a parasitic load or not is to use an ammeter.

I use one of these:



It is a B&K 316 Precision clamp ammeter. It is kind of expensive though and costs around $150.

I also have a less expensive one (MasTech MS2108A), and while it does not have the milliamp reading capability, it still does a good job.

If you decide to purchase a clamp meter, the two things to look for are the resolution (how low of a current they can measure) and if they can do DC (many only do AC).

To check for parasitic loads, zero the meter, then simply clamp the meter around the positive battery lead (the clamp must fully close).

Most clamp meters also have a voltmeter feature, so it is really a handy tool to have.

[Oneilkeys]

Originally Posted by FW28z

Just to clarify a bit, the Red/Yellow/Black power leads on a stereo are pretty much standard.

However, the Yellow wire is a constant source, meaning the radio is always energized when powered. This wire typically is also the main power lead, AND since it is always energized, it also provides memory.

The Red wire goes to the ignition, and puts the radio from standby to active when on. It is not the main (i.e. heavy current carrying) power wire, it is the power switch wire.

The dead giveaway is that the Yellow wire is often (but not always) a heavier gauge wire than the Red wire. Of course, both Red and Yellow need to be energized for the stereo to operate.

The only really good way to determine if you have a parasitic load or not is to use an ammeter.

I use one of these:



It is a B&K 316 Precision clamp ammeter. It is kind of expensive though and costs around $150.

I also have a less expensive one (MasTech MS2108A), and while it does not have the milliamp reading capability, it still does a good job.

If you decide to purchase a clamp meter, the two things to look for are the resolution (how low of a current they can measure) and if they can do DC (many only do AC).

To check for parasitic loads, zero the meter, then simply clamp the meter around the positive battery lead (the clamp must fully close).

Most clamp meters also have a voltmeter feature, so it is really a handy tool to have.

Understand, but when both wires are attached to the same power source and directly to the house batteries, the radio is receiving power all the time and that puts a parasitic load on the house batteries. That is how Thor had mine hooked up. You are right, a good ammeter is the best way to check for parasitic loads, but because of their cost and the infrequent number of times I would use one, I never have purchased one. (I probably wouldn't be able to find it the next time I wanted to use it anyway... Someone would have borrowed it and not returned it.) A poor man's way to check for parasitic loads is to just hook up a volt meter to your battery and see over time, if the voltage drops. I have hard wired a cheap volt meter to my house batteries so I can check how they are doing whenever I want to.

[BCRacing24]

As mentioned my red wire goes to chassis battery. Yellow to coach & black to ground.
This is the correct way to have it hooked up. That way when you switch off your coach batteries your radio audio/channel presets are maintained by the chassis battery that can't be shut off unless disconnected manually at the battery.....

I don't see this as the source of his "parasitic power loss" however. I start my chassis engine once per month during the Winter, never has it been dead. If it's not enough to drain a group 24 chassis battery it certainly won't drain a pair of deep cycle coach batteries. Something else is the phantom source & a meter as described will point it out.

[FW28z]

Granted, there may be more going on than just the stereo's keep alive memory, it's hard to speculate without knowing the actual discharge rate.

The issue I see with using a voltmeter is there is not a lot of difference in a lead acid battery between fully charged and discharged. From fully charged to fully discharged is less than one volt.

It might be hard to detect small parasitic loads quickly with a voltmeter as it might take days to see any change.

There are also significant factors that can affect false readings of battery capacity such as the discharge rate (Peukert's Law), and non-constant loads. Granted, for real small discharge rates, Peukert's Law won't apply.

The most accurate way to measure battery voltage is to remove the battery from the load and let it rest for 24hours.

Perhaps a more consistent method to view the battery state of charge cheaply and not having to disconnect the battery is to measure the battery electrolyte's specific gravity with a hygrometer or better yet, a refractometer (which might be a bit more accurate I suppose).

[Oneilkeys]

Originally Posted by BCRacing24

As mentioned my red wire goes to chassis battery. Yellow to coach & black to ground.
This is the correct way to have it hooked up. That way when you switch off your coach batteries your radio audio/channel presets are maintained by the chassis battery that can't be shut off unless disconnected manually at the battery.....

I don't see this as the source of his "parasitic power loss" however. I start my chassis engine once per month during the Winter, never has it been dead. If it's not enough to drain a group 24 chassis battery it certainly won't drain a pair of deep cycle coach batteries. Something else is the phantom source & a meter as described will point it out.

I solved it. I traded it in on a new one!

[BCRacing24]

LoL

[bevedfelker]

Their reason I asked this question is that before thanksgiving g my coach was at the dealer's for warranty work. They had it for about 4 weeks. The technician had left the use/store switch in USE. When I went to pick up the coach the house batteries were fully discharged.

I always have the use/store in store when the RV is in the storage lot. When I putvthe switch back in USE I have never seen my batteries less than 2/3. I wanted to be sure that the dead batteries were the result of the tech leaving the switch in USE for a significant time period.

Based on this discussion if the next time I check my RV and I put the switch back in USE if my clock time is correct and radio ptesrts are still good I can't assume thevpower to do that came from the house batteries. If the yellow radio wire went to the chassis battery the radio & clock would all be good. Also i have the Axerra not Jensen radio.

In order to check that for sure do I have to track where the yellow wire goes? Is there an easier way?

[BCRacing24]

Put a voltmeter on the yellow wire, disconnect the chassis battery ground. If you lose voltage then that wire is going to chassis battery.

[FW28z]

Originally Posted by bevedfelker

I wanted to be sure that the dead batteries were the result of the tech leaving the switch in USE for a significant time period.

With the use/store switch in the use position, the battery for sure will be under load. There are residual loads such as DC power to the fridge, water heater, furnace, and so on. So the technician leaving the switch into the USE position for 30 days most certainly discharged the batteries.

One thing I have found on my coach, that whenever you connect to shorepower, the battery USE/STORE function automatically goes into USE position - most likely to put a charge on the batteries. But when I disconnect shorepower, the battery stays in USE position.

This makes it very easy to forget to turn the coach batteries off when coming back from camping, a technician doing a repair at the dealership, etc.

[Chance]

Originally Posted by Oneilkeys

....cut.... A poor man's way to check for parasitic loads is to just hook up a volt meter to your battery and see over time, if the voltage drops. I have hard wired a cheap volt meter to my house batteries so I can check how they are doing whenever I want to.

Batteries discharge by themselves even if left disconnected. When parasitic loads are very small, it may be difficult to determine how much of the voltage drop is due to connected load(s) versus normal discharge. It seems to me that you'd have to run your test with battery connected and also disconnected to compare the difference.